There are three main types of antiperspirant stick formulations: compressed powder sticks, gel sticks, and wax sticks. While each of these formulation types may have advantages in certain usage situations, each also has disadvantages. For example, compressed powder sticks are often brittle and hard, leaving a cosmetically-unacceptable powder on the skin upon application. Wax-based formulations can also yield cosmetically-unacceptable products due to such factors as hardness, greasiness, and stickiness. The opacity of such wax sticks and the residue created by their use may also be aesthetically undesirable.
Gel-based sticks have several advantages over both compressed powder and wax sticks. For example, the gel sticks tend to leave little or no residue or dust on the skin. Gel sticks also provide a vehicle which glides easily over the skin's surface resulting in very easy and comfortable application of the product.
Unfortunately, the formulation of antiperspirant compositions in the form of effective and stable gel sticks is difficult. One critical ingredient in antiperspirant gel sticks is the gelling agent. Many known cosmetic gel sticks comprise gelled alcoholic solutions. Gelling agents, such as sodium stearate, are commonly used to form the gel. Such gelling agents cannot be used in the presence of acidic antiperspirant active salts, due to interaction between the gelling agent, which is alkaline, and the antiperspirant active.
Gelling agents which are more useful in the preparation of antiperspirant gel sticks are the dibenzylidene alditols. For example, dibenzylidene sorbitol (DBS) is a well-known gelling agent. See, for example, U.S. Pat. No. 4,154,816, Roehl et al., issued May 15, 1979; U.S. Pat. No. 4,816,261, Luebbe et al., issued Mar. 28, 1989; and U.S. Pat. No. 4,743,444, McCall, issued May 10, 1988. Various substituted dibenzylidene alditol gelling agents have been found to be of benefit in antiperspirant gel sticks since they can exhibit improved stability in the acidic environment of the antiperspirant gel stick, and consequently improve shelf life of the product.
Japanese Published Application 64-62377, Kao, published Mar. 8, 1989, describes fluorinated dibenzylidene polyhydric alcohol derivatives which are effective gelling agents for cosmetic compositions containing a wide range of organic solvents.
U.S. Pat. No. 4,429,140, Murai et al., issued Jan. 31, 1984, discloses a method for producing DBS and its derivatives. Disclosed DBS derivatives include those where the benzene ring is substituted with from 1 to 3 lower alkyl groups, lower alkoxy groups, halogen atoms or nitro groups.
U.S. Pat. No. 4,371,645, Mahaffey, issued Feb. 1, 1983, describes plastic compositions which include DBS derivatives for improved transparency. These DBS derivatives must include a chlorine or bromine substituent in the meta and/or para positions and may also include lower alkyl, hydroxy, methoxy, mono- or dialkyl amino, or fluorine substituents. Di(para-chloro) DBS, di(para-fluoro) DBS, and di(para-methoxy) DBS are all specifically disclosed.
European Patent Application 0286522, Roquette Freres, published Dec. 1, 1988, describes a process for making high purity alditol diacetals. Para-chloro DBS is disclosed.
DBS-type compounds found to be particularly useful for antiperspirant gel sticks are disclosed in U.S. patent application Ser. No. 07/696,377, "Gel Stick Antiperspirant Compositions", Oh, Juneja, and Connor, filed on May 6, 1991, the same filing date as the present patent, and its parent application Ser. No. 07/505,807, Oh, Juneja, and Connor, filed Apr. 6, 1990 Disclosed are substituted dibenzylidene alditols that are derivatized at the meta position of the benzene rings. Exemplary compounds include di(meta-fluoro) DBS and di(meta-chloro) DBS. These meta-substituted dibenzylidene alditols have improved stability in acidic conditions.
During processing and manufacture of antiperspirant gel sticks containing dibenzylidene alditol gelling agents, it is necessary to solubilize the gelling agent in a solvent, typically a monohydric or polyhydric alcohol. In order to do this, it is necessary to heat the ingredients to a temperature which is high enough to induce solubilization and which is also above the gel point of the gelling agent/solvent solution. Unfortunately, the relatively high temperatures required tend to cause even the best dibenzylidene alditol gelling agents to degrade in the presence of the acidic antiperspirant active, or other acidic material. Accordingly, there is a need to provide antiperspirant gel stick compositions containing benzylidene alditol gelling agents that can be made at reduced processing temperatures. This can provide reduced decomposition of the dibenzylidene alditol gelling agent during processing, and provide more efficient utilization of gelling agent in the final product. The ability to farm the gels by processing at lowered processing temperatures also can reduce by-products and improve stability and processing of other ingredients typically included in antiperspirant compositions, e.g., perfumes and other volatile components, as well as improve compatibility with plastic packaging into which heated molten antiperspirant compositions may be added. There is further a need to provide a process for making such antiperspirant gel stick compositions.
Various attempts have been made in the past to meet these objects. For example, in U.S. Pat. No. 4,719,102, Randhawa et al., issued Jan. 12, 1988, it is disclosed to prepare an antiperspirant gel stick containing an acidic antiperspirant active, a dibenzylidene monosorbitol acetal gelling agent, alcohol solvent, and an organic compatible solvent of not greater than about five carbon atoms which is a good hydrogen bond donor or acceptor. Cyclic esters, amides, amines, ketones, ureas, carbamates, sulfoxides, and sulfones are discussed. More particularly, such materials as lactones, lactams, cyclic ketones, urea, cyclic carbamates, cyclic sulfoxides, cyclic sulfones, and their open chain analogs having no more than five carbon atoms are discussed. Specific examples are morpholine, pyridine, acetic acid, ethylene carbonate, propylene carbonate, N-methyl pyrrolidone, pyrrolidone, butyrolactone, dimethylsulfoxide, dimethyl formamide, 2-ethylethanol, and caprolactam. In U.S. Pat. No. 4,722,835, Schamper et al., issued Feb. 2, 1988, it is proposed to incorporate into an antiperspirant stick a small, polar organic compound in combination with the dibenzylidene monosorbitol acetal gelling agent, antiperspirant active, a basic metallic salt, and an alcohol cosolvent. The small, polar organic compound is morpholine, pyridine, acetic acid, ethylene carbonate, propylene carbonate, N-methyl pyrrolidone, pyrrolidone, butyrolactone, dimethylsulfoxide, dimethylformamide, 2-ethoxyethanol, and caprolactam. Whereas the compositions of these patents are said to be able to be processed at reduced temperatures, the exemplified solvents added to reduce processing temperature unfortunately tend to either cause off-odors in the final product, are not stable under acidic conditions, or present skin compatibility issues, such as (but not limited to) skin irritation. Thus it remains desirable, and it is an object of this invention, to provide compositions and a method of making them, which exhibit a combination of significantly reduced processing temperature requirements without incurring the disadvantages associated with prior known compositions.
It is also an object of this invention to provide compositions and a method for making them, as described above, which provide effective gels for use in antiperspirant applications, and which can provide both good antiperspirant efficacy and cosmetic characteristics.
The present invention provides antiperspirant compositions containing particular cosolvents used in combination with hydroxy solvents (such as mono- and polyhydric alcohols) in benzylidene alditol-containing antiperspirant gel stick compositions which enable the compositions to be made at reduced temperatures. Specifically, the 2-oxazolidinone compounds have a lower alkyl (e.g., C.sub.1 -C.sub.4) substituent located at the 3 position of the heterocyclic ring. The present invention also provides a method of making such compositions, by which processing temperature can be reduced relative to processes not including the selected 2-oxazolidinone cosolvent.
The use of 2-oxazolidinone compounds as cosolvents in dibenzylidene alditol-containing gel stick compositions can lower the processing temperature required, and consequently can reduce gelling agent degradation during processing. They can also improve the gelling agent efficiency and the gel characteristics in the final product.
2-oxazolidinone compounds are disclosed for use in various applications, such as electro-chemical applications, e.g., U.S. Pat. No. 3,951,685, and Japanese Patent JP 61 55,196 (1985). They also have been disclosed, for example, as being useful as antiwear/antioxidant compounds for lubricants in electronic devices, e.g., JP 6155196 (1986), and as a topical mosquito repellent, e.g., "Topical Mosquito Repellents X: 2-Oxazolidones", A. Skinner, H. T. Crawford, D. Skidmore, and I. Maibach, J. Pharmaceutical Sciences, Vol. 66, No. 4, April 1977, pp 587-589. 2-Oxazolidinones are also described, for example, in "Liquid 2-Oxazolidones. 1. Dielectric Constants, Viscosities, and Other Physical Properties of Several Liquid 2-Oxazolidones", H. L. Huffman, Jr. and P. G. Sears, J. Solution Chemistry, Vol. 1, No. 2, 1972, pp 187-196, and as solvents, detergents, pigments, dye compositions, polymers, and chemical intermediates. Whereas patents to Schamper et al. and Randhawa et al., referenced above, very generally mention cyclic carbamates, i.e., 2-oxazolidinones, they do not disclose the 3-(alkyl)-substituted 2-oxazolidinones hereof nor suggest the necessity of the alkyl substituent at the 3 position of the heterocyclic ring for fulfilling the objects here for a stable, efficacious, and skin compatible antiperspirant gel stick.